When inspecting a Pokemon I've captured, some have "progress" made on the bar behind the Pokemon's portrait, however some do not. For example, I have four Drowzee – at 12, 13, 14 and 72 CP. The one with 72 CP has over half of the bar filled, while the other three do not have any of the bar filled.
Now I also have a Rattata at 35 CP, who has a similar amount of progress made on the bar – even though it as it a significantly lower CP.
Since the bar does not appear to be proportionate to a Pokemon's CP (contrary to comments), what does this bar mean, how do I fill it, and what happens when it fills up?
Best Answer
The bar above a Pokemon represents their CP in a relative range, for that specific species.
The lower end of this bar represents some (still unknown) minimum value for a single species. The higher end of this bar represents the maximum CP this Pokemon can have at your current Trainer level.
For example, Rattatas are rather weak, therefore their CP range is a lot smaller than that of a Drowzee, which explains the bar difference you are seeing.
You may fill the bar up by training your Pokemon. Note that absolutely nothing happens to the Pokemon when you fill the bar -- you've just reached the Pokemon's current CP cap.